Types of Hoists
A hoist is a mechanical device that lifts, lowers or transports objects by means of a cable which wraps around a wheel. Passing the cable through the wheel gains a mechanical advantage which enables the hoist to lift heavy objects with comparative ease. Hoists receive extensive use in industry, auto repair and caring for the disabled. Various types of hoists, with different kinds of cable and different power sources exist, since hoists serve many purposes.
Chain hoists use metal interlocking chains for the cable or lifting mechanism. Chain hoists are the most popular type of hoists for lifting objects 7.5 tons or less. For loads heavier than this, another type of lifting mechanism, wire rope, is more common. Chain hoists generally require less maintenance, and chain can last 30 times longer than wire rope.
Wire rope is the other prevalent type of cable used in hoists. Wire rope consists of individual strands of wire wrapped around a core. Wire rope is usually made from carbon steel, and hoists with this type of cable are often used to lift heavier loads than chain hoists lift. Wire rope hoists also have faster lifting speeds than chain hoists, although, on the down side, they are also more expensive.
Hoists also have different power sources as along with different types of cable. The oldest type of hoist, one that has been used for may centuries is the manual hoist. Humans, animals, even water are power sources for manual hoists; however, although some manual hoists remain in use, generally they have been superseded by more powerful motor powered devices.
Electric powered hoists are the most common hoists in use today. Since one person can operate an electric hoist, and an electric hoist can do the work of many employees, many businesses use them as a cost saving device. An electric hoist might be industrial strength for use in manufactured housing, lumber mills and plastic manufacturing or a smaller, portable device that can assist in moving the elderly and disabled.
Pneumatic hoists or air powered hoists offer some advantages over electric powered hoists. They can weigh 40 percent to 50 percent less than electric hoists, making them easier to install, and typically are simpler to repair. They do not pose a risk of electric shock if the power cord is damaged and can tolerate higher temperatures. Pneumatic hoists have greater resistance to dirt, dampness and weather than electric hoists and do not need surge protectors to guard against voltage spikes. A disadvantage of air powered hoists is that speed and position control is more difficult.